Method of distributing siliceous fillers uniformly throughout a water-laid web while the web is on the fourdrinier wire



R. O. TREAT METHOD OF DISTRIBUTING SILICE Nov. 22, 1966 3,287,207

ous FILLERS UNIFORMLY THROUGHOUT A WATER-LAID WEB WHILE THE WEB IS ONTHE FOURDRINIER WIRE Filed April 17, 1964 2 sheets-sheet 1 INVENTORRALPH O. TREAT Nov. 22, 1966 7 2 OT mw ,wEm 7HRS 8mm 20 t ,RRe mmm MT &-4% o ww Z Um B .V N M N @N RW B O Wow 0 R. m 9m LAID WEB WHILE THE vLnzw METHOD OF DISTRIBUTING SILICE A WATER- Filed April 1.7; 1964 UnitedStates Patent METHOD OF DISTRIBUTING SILICEOUS FILLERS UNIFOI-ZMLYTHROUGHOUT A WATER-LAID WEB WHILE THE WEB IS ON THE FOURDRIN- IER WIRERalph 0. Treat, Havre de Grace, Md., asslgnor to J. M. HuberCorporation, Locust, N.J., a corporation of New Jerse y Filed Apr. 17,1964, Ser. No. 360,582

3 Claims. (Cl. 162-186) This invention relates to a novel method ofadding inorganic fillers to paper.

Paper is formed in modern paper mills by depositing fibers on papermachine wire. This is accomplished by forming a furnish of cellulosicfibers in water with retention aids, pigments, flocculating agents,binders and other additives used in papermaking.

The furnish is initially about 95 to 99% water. After treating thefurnish to achieve the proper formulation it is contacted with the papermachine wire. The cellulosic fibers are deposited on the wire as aresult of gravity and applied vacuum which pulls the water through thewire and deposits the fibers uniformly on its surface.

Fourdrinier machines utilize table rolls, suction boxes, and suctioncouch rolls to aid in water removal. If the suction is increased at anyof these points, an increase in drainage occurs with a resultant compactsheet.

Fibers are deposited by gravity or suction on cylinder machines with thehead caused by the difference in liquid levels inside and outside thecylinder mold.

Generally, filled or pigmented papers are made on the Fourdriniermachine.

There is a short interval, at the beginning of the run on theFourdrinier, during which the finely divided matter such as fillers,fibers and additives, passes practically unhindered through the wire.Soon thereafter, a mat starts to form on the wire and drainage of thewater has to take place through this mat.

The efliciency 'of the mat as a filter depends among other things uponits thickness, the nature of the fibers, and the speed of the wire. Toomuch suction or vacuum on the table roll, the suction boxes, and suctioncouch roll may be responsible for sucking loose some of the fineparticles of filler and fiber which have been deposited in the sheet,resulting in a condition known as two sided ness.

The retention of the fine colloidal or near colloidal matter such asinorganic fillers presents a problem because they are finer than thepores in the wet fiber mat. This is a problem of economic importancebecause for the most part the pigments and fillers constitute the mostexpensive part of the paper furnish.

As a rule, inorganic fillers are added to the furnish in the beater orfan pump and travel from there to the head box along with the furnish.From the head box, the furnish is flowed onto the wire to form the web.This type of paper making process destroys functional aggregates in lowrefractive index pigments, thus reducing efiiciency for developingoptical properties and creates problems of filler retention as well asfiber fines retention, two sidedness or unequal brightness between thewire and felt sides of the sheet. This process also requiresconsiderable time for the system to equilibrate, resulting in fillerlosses at the start and finish of a run.

Another process by which attempts have been made to eliminate theseproblems is that in which fillers have been added directly to the web.

This is accomplished by spraying the filler onto the :lip of the headboxor slice, or further downstream on a deflector with a lip. By thisprocess, the filler contacts the web and generally deposits on thesurface thereof.

The water is removed from the web beneath the surface on the wire sideleaving the filler undisturbed. This, of course, results in extreme twosidedness caused by unequal distribution of the filler.

The primary object of this invention is to provide a method foreconomically and efliciently filling paper with inorganic fillerpigments.

Another object of this invention is to provide a method of producingfilled paper with a minimal two sided effect.

A further object of this invention is to provide a method of fillingpaper that results in an even distribution of the filler throughout thefinished paper.

A still further object of this invention is to provide a method offilling paper with inorganic filler pigments whereby the optimumaggregate size in the fine particle low refractive index pigments isretained.

Other objects and advantages of this invention will become apparent fromthe following specification taken in the light of the drawings in which:

FIGURE 1 is a schematic drawing of a typical spray distribution systemused in this invention,

FIGURE 2 is a view of the spray nozzles in relation to the papermachine,

FIGURE 3 is a view of the spray system, and

FIGURE 4 is the cutaway view of the spray line.

I have discovered that an aqueous slurry of a paper filler pigment canbe sprayed into the moving Web at a particular location on the equipmentand under special conditions to insure an even distribution of thepigment throughout the paper. This accomplishes the desirable result ofminimal two sidedness and immediate high pigment retention.

Referring now to the drawings in detail wherein like referencecharacters indicate like parts throughout the several figures, thereference numeral 1 indicates a filler storage tank in a paper makingsystem in which an aqueous slurry of paper filler is stored. A slurryfeed line 2 extends from the tank 1 through a valve 3 to a spray feedpump 4. Filler slurry is pumped by the spray feed pump 4 through itsdischarge feed line 5 into a screen strainer 6. The outlet from thescreen strainer 6 is controlled by a valve 7 and the filler slurrypasses from the valve 7 through a line 8 to a concentric reducer 9. Ahorizontal spray distribution pipe 10 is positioned above the wire of apaper making machine and extends perpendicular to the direction oftravel of the wire in the machine.

The spray distribution pipe 10 has a pressure gauge 11 mounted thereonand is further provided with a plurality of depending spray nozzles 12communicating therewith. An eccentric reducer 13 is secured to the endof the pipe 10 opposite the concentric reducer 9 and has a recycle line14 extending therefrom to a throttle valve 15. A drain hose 16 extendsfrom the throttle valve 15 and is arranged to discharge into the tank 1or selectively into the sewer. A flush Water line 17 extends from asource of water under pressure through a valve 18 into the line 2between the valve 3 and the pump 4. Flushing water provided through theflush Water line 17 is used when the paper making run has been completedand it is necessary to flush the filler slurry from the lines.

As can be seen clearly in FIGURE 2, the filler slurry spray from thespray nozzles 12 is directed at the moving web 20 from a distance offrom 6 inches to 4 feet above the web 20 depending upon the speed of thewire 21 and the pressure of spray. The spray can be a hollow cone as isshown in FIGURE 1 at 19 and is representative of the type of spraypattern which is obtained when using low pressures of about 3 to 20p.s.i.g. The spray nozzles 12 are spaced apart on the spray distributionpipe 10 such that the sprays from each of the nozzles 12 intersectadjacent sprays to form the spray pattern 3 19 which can be described asa first series of circles in tangential relationship upon which a secondseries of tangential circles of the same size are superimposed with thecenters of these circles at the point of tangency of the circles in thefirst series.

The spray nozzles 12 are arranged so that they extend completely acrossthe width of the wire 21.. The spray is directed to the web 20. as shownin FIGURE 2 at a point from 3 to 12 feet upstream from the first vacuumbox 22. On conventionally used machines this is usually the fourth tosixteenth table roll 23 depending on the speed of the wire 21 as Well asthe point at which the web consistency is such that optimum fillerretention and optical proper-ties are obtained. in the paper.

By means of this process the filler strikes and is drawn into the webwhere it contacts the fibers and fibrils of the paper and becomesattached thereto by physical and/or chemical means.

The filler particles used in this invention are much smaller in sizethan the space between the paper fibers and would normally be expectedto be drawn completely through the web by a process such as thatcontemplated by the present invention. Since this does not occur whenfollowing the process as described it is theorized that a surfaceattraction between the filler and cellulosic fibers and fibrils occurs.I

To avoid extreme two sidedness and excess filler losses it is necessarythat the filler contact the web when the solids content of the web issuch that the filler is able to be drawn into it by suction and beevenly distributed. If the filler contacts the web too near the headbox,it is drawn completely through the web with large filler losses. If thefiller is sprayed onto the web too far downstream, the web is too dryand the filler only coats the top surface of the web. Some of thisfiller from the top surface is lost due to dusting after the paper hasdried.

At spray heights of from 6 inches to 4 feet and spray pressures of from3 p.s.i.g. to 20 p.s.i.g. good results are obtained at from 3 to 12 feetupstream from the first vacuum box. The concentration of the fillerslurry should be such that it can be atomized by the spray nozzle. Themos-t effective filler concentrations are from 0.5 lb./gal. to 2 lbs./gal. or about to 20% solids. The speed of the wire determines thespecific heights and spray pressures of the nozzles as well as theirlocation. Within the limits defined, machine speeds of from 1000 to 3000feet per minute are operable.

The pigment fillers useful in this process are inorganic siliceouspigments of fine particle size, usually within the 0.01 to 0.6 micronrange. The siliceous pigments with silanol groups on the surface thereofare those most advantageously used since they have a tendency to attachchemically as well as physically to the cellulosic fibers, assuring evendistribution throughout the paper with high retention.

These pigments can be characterized as those amorphous siliceouspigments containing at least 50% SiO and at least 3.5% bound water. Theycan be made by precipitating Si0 from sodium silicate by means of acidsor in the' manner described in US. Patents 3,034,913 and 3,034,914wherein sodium silicate is partially neutralized with acid and silica isthereafter precipitated therefrom with an acid salt such as calciumchloride or alum.

Other suitable siliceous fillers are made by precipitating silica fromcalcium silicate with acid in the the manner described in US. Patent3,110,606.

Another suitable siliceous filler is calcium silicate prepared by ahydrothermal pressure reaction of lime and Other conventionally usedfillers for newsprint and other. lightweight papers can be used in thisinvention; for ex-.

ample clay or calcium carbonate. Combinations of siliceous fillers arealso suitable, for example, mixtures of silica and sodium aluminosilicate.

The pH of the reaction medium,,as well as the pre-. cipitating pH, andthe type of silicate used are among the factors which determine thespecific sodium alumino silicate produced. A variation in these factorsdetermines.

the molar ratios of the oxides of sodium, aluminum,

and silicon, as well as the particle size, specific gravity,

and surface area of the pigment. Pigments with molar ratios of above 0.8mole of Na O per mole of A1 03 and 1 over 4 moles of Si0 per mole of NaO with a particle size of less than 0.14 micron in diameter, aspecific'gravity I v of 2.10 to 2.26 and a surface area greater than 20square meters per gram are useful in the practice of this invention.

The following examples and tables illustrate the prac:

tice of this invention and are not intended to limit the invention.

Example 1 A Fourdrinier paper machine with a speed of 2,000

ment was sprayed on the moving web at a pressure of 7 Sufficient pigmentwas One point of application was at the first fiatbox. A second pointwas at the sixth table roll and the third point was at the 16th tableroll. The results are shown in Table I.

ExampleZ Using the same speed machine sodium alumino silicate filler wasapplied under 10 p.s.i.g. at the first table roll and under 15 p.s.i.g.at the 2nd, 4th, 6th, and 12th table rolls. The results are shown inTable II.

Example 3 spray was 18 inches. applied was varied on the different runs.It was applied at the 4th, 6th and 8th table rolls during successiveruns. The results are in Table III.

TABLE I.-32-LB. STANDARD NEWSPRINT Percent Laroc ue Percent PolntApplied Pressure, Percent Percent Percent smoothness, Brightness,Percent Strike Through, Printap.s.i.g. Applied Retained Retention W/FW/F Opacity at 2.0 gJm. ink bility pick up Unfilled- /92 58. 2/58. 0 90.7 12 1st flatbox. 7 3. 26 1. 88 57. 7 61. 0/58. 5 91. 5 9. 7 S 6th tableroll 7 3. 26 2. 52 77. 2 92/85 61. 6/59. 4 92. 8 8. 5 84. 5 16th tableroll 7 3. 26 3. 15 96. 6 87/79 62. 5/59. 6 92. 9 7. 7 84. 3

TABLE lI.33-LB. OFFSET NEWSPRINT Pressure, Percent Percent PercentBrightness, Percent Percent Percent Point Applied p.s.i.g. AppliedRetained Retention W/F Opacity Larocque Printability Strike Through U fi58/58. 3 90. 5 12. 84. 1st table roll. 2. 38 2. 30 96. 5 61. 8/59. 1 92.3 9. 8 85. 0 2nd table roll 3. 08 2. 39 77. 5 62. 0/59. 4 92. 1 8. 6 84.5 4th table roll 15 3. 08 3. 03 98. 5 62. 2/59. 2 91. 8 9. 0 84. 2 6thtable roll 15 3. 08 2. 74 89. 0 61. 9/59. 2 92. 0 9. 8 84. 7 12th tableroll.. 15 3. 08 2. 22 72. 2 62/59. 5 91. 6 8. 5 84. 5

The data in Tables I and 11 indicate that when the filler pigments aresprayed onto the moving web, they effectively fill the paper and theoptimum positions for spraying 3 p.s.i.g. to about p.s.i.g. from spraynozzles positioned above the moving web and intermediate the headbox andthe first vacuum box of the papermaking machine wherein on the machinesused is from the sixth to the sixteenth 15 the solids content of themoving web is such that the filler table roll for Example 1 and at thefourth to the sixth is uniformly drawn substantially completelytherethrough table roll for Example 2. It is possible to determine theand is substantially completely retained therein, thereby optimum pointof contact for any machine used in a distributing said filler pigmentuniformly throughout said similar manner. moving web.

TABLE III Percent Larce- Percent Percent Percent que Strike ANPA Print-Point Applied Percent Ash Loading Brightness, Opacity Mullen, p.s.i.Through at ability, W/F

WI]? 2.0 Jm. Ink Pick Up, W/F

o. 52 57. 5/ s. 0 90. 5 6. 2 13. 0/11. 0 85. 7/84. 5 2. 4s 2. 10 60. 1/9. 1 93. 3 7. 1 9. 1 7. 5 85. 5/84. 5 3. 06 2.78 60. 5/59. 5 93. 0 6. 39. 2/7. 4 85. 1/84. s 8th table roll 2. 4o 2. 05 59. 1/59. 0 92. 9 s. 610. 5/7. 5 85. 5134. 3 Internally Filled (Headbox) 2.50 2. 11 59. 0/59.4 91. 5 7. 2 8.7/7.0 85. 0/84. 2

The data indicates that beneficial properties are imparted to the paperwhen the filler pigment is sprayed on the moving web. With the machineused as shown in Example 3, the data indicates that the point of optimumresults is at or near the 6th table roll which is about 6 to 7 feetupstream from the first vacuum box. The data illustrates the fact thatthe optical properties of internally filled paper are somewhat less thanthe paper filled by the process of this invention while the printproperties are equivalent.

The examples indicate the feasibility of the process and the dataindicates the beneficial results imparted to the paper in terms ofbrightness, opacity and printability as well as pigment retention. Sinceit is obvious that the invention can be practiced on equivalent machinesand under different conditions it is not intended that it be limited bythe examples but only by the scope of the appended claims.

I claim:

1. A method of distributing siliceous filler pigments of a particle sizeof from 0.01 to 0.6 micron substantially uniformly throughout a movingweb on a Fourdrinier papermaking machine which consists essentially ofspraying an aqueous slurry of said filler pigments to said moving 55 webfrom a height of from about 6 inches to about 4 feet above the movingweb at a spray pressure of from about 2. The method of claim 1 whereinsaid spray is directed toward the moving web from a series of spraysessentially perpendicular to the direction of travel of the web at leastabout 3 feet upstream from the first vacuum box on the papermakingmachine, and wherein the spray pattern is a hollow cone pattern.

3. The method of claim 1 wherein the speed of the moving web is aboutfrom 1000 feet per minute to about 3000 feet per minute.

References Cited by the Examiner UNITED STATES PATENTS 2,054,630 9/ 1936Hurrey 162186 X 2,062,563 12/1936 Fair 162-186 2,112,540 3/ 1938McAndrews et a1. 162186 2,373,914 4/1945 Quinn 162-l86 X 2,426,043 8/1947 Muggleton 162186 2,943,970 7/1960 Allen 162-181 3,034,913 5/ 1962Lagerstrom 162181 FOREIGN PATENTS 720,006 12/1954 Great Britain.

DONALL H. SYLVESTER, Primary Examiner, EO A HO E. E mi r.

1. A METHOD OF DISTRIBUTING SILICEOUS FILLER PIGMENTS OF A PARTICLE SIZEOF FROM 0.01 TO 0.6 MICRON SUBSTANTIALLY UNIFORMLY THROUGHTOUT A MOVINGWEB ON A FOURDRINIER PAPERMAKING MACHING WHICH CONSISTS ESSENTIALLY OFSPRAYING AN AQUEOUS SLURRY OF SAID FILLER PIGMENTS TO SAID MOVING WEBFROM A HEIGHT OF FROM ABOUT 6 INCHES TO ABOUT 4 FEET ABOVE THE MOVINGWEB AT A SPRAY PRESSURE OF FROM ABOUT 3 P.S.I.G. TO ABOUT 20 P.S.I.G.FROM SPARY PRESSURE OF FROM ABOUT ABOVE THE MOVING WEB AND INTERMEDIATETHE HEADBOX AND THE FIRST VACUUM BOX OF THE PAPERMAKING MACHINE WHEREINTHE SOLIDS CONTENT OF THE MOVING WEB IS SUCH THAT THE FILLER ISUNIFORMLY DRAWN SUBSTANTIALLY COMPLETELY THERETHROUGH AND ISSUBSTANTIALLY COMPLETELY RETAINED THEREIN, THEREBY DISTRIBUTING SAIDFILLER PIGMENT UNIFORMLY THROUGHOUT SAID MOVING WEB.